The field of art to which this invention pertains is organophilic clays and preactivators therefor.
Organic compounds which contain a cation can react by ion exchange with clays having platelets in a negative layer-lattice and having exchangeable cations. If the organic cation contains at least one alkyl group having at least 10 carbon atoms, the resulting modified clay has the property of swelling in certain organic liquids so as to modify the rheological properties of the liquid. Organophilic clays have been described in a large number of patents, one of the earliest being U.S. Pat. No. 2,531,427.
In order to achieve the desired rheological properties of thickening and/or gelling the organic liquid, e.g., the formation of lubricating greases from liquid hydrocarbons, it is necessary that the organophilic clay be thoroughly dispersed in the liquid.
One method of obtaining proper dispersion and activation of the organic organophilic clay is to use polar activators, dispersants, dispersion aids, solvating agents, and the like as disclosed in U.S. Pat. No. 4,664,820 as well as U.S. Pat. Nos. 2,677,661; 2,704,276; 2,833,720; 2,879,229; 2,966,506; and 3,294,683. Examples of such compounds are acetone, methanol/water, ethanol/water, propylene carbonate, acetonylacetone, diacetone alcohol, dimethyl formamide, and gamma-butyl lactone. Such compounds are liquid and are added along with the organophilic clay to the organic liquid.
Another method for obtaining readily dispersible organophilic clays is to preactivate the clay by blending it with an additive. The use of finely divided solid alcohols, such as neopentyl glycol, 2-methyl-2-propanol, erythritol, monopalmitate glycol, and the like, is disclosed in U.S. Pat. No.4,435,218.
In U.S. Pat. No. 4,664,820, the use of such compounds as phthalide, 3-hydroxy-4-methoxy benzaldehyde, 4-benzyloxypropiophenone, triethyl citrate, 2-phenoxy-ethanol, 1-phenyl-1,2-ethanediol, nitrobenzyl alcohol, 1,6-hexanediol, castor oil, and nitrophenethyl alcohol are disclosed as preactivators for organophilic clays.
Other patents which disclose preactivators for organophilic clays are U.S. Pat. 3,937,678 and U.S. Pat. No. 3,977,894. The preactivators described in these patents are amide waxes and a mixture of an amide wax and glyceryl tri-12-hydroxystearate.
Organophilic clays having enhanced dispersibility have been made by subjecting the clay before or during the reaction with the organic cation to shear conditions which deagglomerate the clay particles. Patents which disclose these physical treatments are U.S. Pat. No. 3,951,850; 4,623,398; 4,695,402; 4,664,842; 4,743,305; and 4,664,820.
In U.S. Pat. No. 4,743,306, a mixture of clay and finely divided silica is reacted with an organic cation to form organophilic clays having improved dispersibility.
As disclosed in U.S. Pat. No. 4,382,868, organophilic c of improved dispersibility are prepared by extruding a mixture of clay, organic cation, water and alcohol, and thereafter grinding the extrudate without drying the water and alcohol.
Although polar activators, which are added along with the organophilic clay to the organic liquid, are efficient dispersion aids for the organophilic clay, the preactivators are preferred in industrial applications. The use of preactivated clays by the manufacturer eliminates the additional step of having to add the polar activator, eliminates a source of measurement error, and reduces the amount of hazardous chemicals to be handled.
Preactivators for organophilic clays are generally dry, waxy solids which are dry blended with the organophilic clay. Liquids are generally not used as organophilic clay preactivators because they cannot be readily dispersed uniformly throughout the clay and because clays treated with such liquids are not free-flowing and are difficult to handle.